1. Field of the Invention
The present invention relates to a passive latching system for connector housings.
2. Description of the Prior Art
As connectors get smaller the force required to withdraw a terminal mounted in a first connector housing from a mated terminal mounted in another connector housing is reduced. Concomittant with this reduction in the withdrawal force is the need to provide a supplementary holding force that assists in retaining the housings together. Passive latch systems have been useful for this purpose in situations, as in small connectors, where space availability is at a premium.
U.S. Pat. Nos. 4,787,860 (Bender); 4,900,263 (Manessero et al.); 4,925,398 (Samejima et al.); and 4,938,710 (Aihara et al.) each exemplify a passive latching system for connecting a pair of connectors. Shown in FIG. 1 is a schematic illustration of the basic functional elements of a passive latching system useful to interconnect a first connector housing H.sub.1 with a second connector housing H.sub.2. The housings H.sub.1 and H.sub.2, which generally represent any two connector housings, are inserted into mated relationship in the direction of the arrow M (latching direction) and withdrawn from the mated relationship in the direction of the arrow W (unlatching direction).
The passive latching system includes a projection P mounted on the housing H.sub.1. The projection P is received in a complementary aperture A formed in the housing H.sub.2. The projection P is defined above a reference surface R.sub.1 on the housing H.sub.1 by raised working surfaces S.sub.p1, S.sub.p2. The surface S.sub.p1 forms a sloped lead-in ramp while the surface S.sub.p2 defines a sloped exit ramp. The slopes are taken in the x-z plane and are defined with respect to the reference surface R.sub.1. These slopes are indicated by the respective characters m.sub.in, m.sub.e. The slopes need not necesarily be equal. The projection P may take any of a variety of forms and may include the flat surface S.sub.p3, if desired. The edge between the working surface S.sub.p2 and the reference surface R.sub.1 is indicated by the character E.sub.p. The free edge of the surface S.sub.p2 lies a distance h above the surface R.sub.1.
In complementary fashion the aperture A is defined by a depression extending below a reference surface R.sub.2 formed on the housing H.sub.2. (In FIG. 1 the reference surface R.sub.1 is defined on what appears as the "top" of the member indicated as H.sub.1 while the reference surface R.sub.2 is defined on what appears as the "bottom" of the member indicated as H.sub.2. The relative position of the members H.sub.1, H.sub.2 may be inverted, if desired.) The aperture A is defined by a plurality of surfaces, at least one of which defines a working surface S.sub.a. The aperture of which the surface S.sub.a forms a part may take a variety of forms, including an enclosed recess as illustrated in FIGS. 1, 2B through 2G, 3D through 3I, 4A and 4B, or a partially enclosed slot, as illustrated in FIGS. 4C and 4D. The edge between the working surface S.sub.a and the reference surface R.sub.2 is indicated by the character E.sub.a. It is noted that the edges E.sub.p and E.sub.a extend perpendicular to the latching direction M (and to the unlatching direction W).
As the housing H.sub.1 is advanced into the housing H.sub.2 (in the direction of the arrow M) the lead-in ramp formed by the working surface S.sub.p1 on the housing H.sub.1 lifts the reference surface R.sub.2 on the housing H.sub.2. The housing H.sub.1 is advanced until the projection P enters into aperture A. The working surface S.sub.a then snaps behind the raised working surface S.sub.p2 thus latching the housing H.sub.1 to the housing H.sub.2. An audible clicking sound usually accompanies the latching of the housings.
When the parts are to be separated the process is reversed. The housings H.sub.1 and H.sub.2 are relatively moved in the direction of the withdrawal arrow W (unlatching direction). In this instance the portion of the raised working surface S.sub.p2 along the edge E.sub.p thereof engages along a line of contact with the edge E.sub.a of the aperture A in the housing H.sub.2. The line of contact between the working surface S.sub.p2 and the edge E.sub.a exists over a length portion D (shown as measured along the reference surface R.sub.1) during the withdrawal of the housings. Thus, a relatively substantial force acting in the direction of the arrow W may be required to lift the reference surface R.sub.2 as the housings are withdrawn from each other.
In view of the foregoing it is believed advantageous to provide a passive latching system that requires a reduced withdrawal force to separate the mated housings.